The multimedia messaging service is a communication service under development in which a terminal of a cellular network can send multimedia messages to another terminal. The content of a multimedia message may be e.g. a video clip, an audio clip or a combination of these. The transmission service of multimedia messages in connection with the WAP system (Wireless Application Protocol) is defined in the standard specifications WAP-206MmsMessagingService and WAP-209-MMSEncapsulation. In the third-generation mobile communication networks the multimedia messaging service is to be implemented in a similar manner. In the transmission of a multimedia message the terminal transmits the multimedia message wirelessly to a base station in the cellular network, which forwards the message to a multimedia message service centre MMSC. Having received the multimedia message, the MMSC transmits a notification message to the terminal to which the multimedia message is addressed. Having received the notification message, the terminal software decides whether to fetch the multimedia message. If the terminal (or its user) decides to fetch the multimedia message, the terminal can send a WSP GET request (Wireless Session Protocol) to the MMSC. The MMSC receives this request and transmits the multimedia message in question to the terminal. In a typical case the multimedia message is transmitted to the terminal automatically without user intervention, substantially according to the store-and-forward transmission. The MMSC, however, sends a notification message to the terminal before the multimedia message is transmitted, and the decision on whether to allow transmission of multimedia messages from the MMSC to the terminal is made at the terminal.
In a normal situation the MMSC transmits a notification message to the terminal as soon as a multimedia message addressed to the terminal in question arrives. However, the MMSC may fail to transmit the notification message for several reasons and the terminal may fail to receive it. For example, if the terminal is switched off, it cannot receive notification messages. In addition, the memory of the terminal can be temporarily so full that there is no room for the notification message sent by the MMSC, or an error may occur on the transmission path as a result of which the notification message gets lost on its way to the terminal. It may also happen that the notification message arrives at the terminal, but the terminal cannot interpret it due to an error on the transmission path.
In addition to the above-mentioned reasons, the terminal may fail to receive the notification message because of poor connections. The radio signal that includes the notification message may be too weak when it arrives at the terminal. The battery of the terminal may be so low that the notification message cannot be received. The following situation exemplifies this. The terminal is in standby mode as the notification message arrives at the terminal. The terminal shifts from the standby mode to the reception mode and simultaneously its power consumption increases. Since the battery is, however, almost dead, increase of power consumption switches the terminal off, and thus the terminal cannot receive the notification message.
If the short message service (SMS) is used as the transmission path for the notification message, the terminal may be transmitting several messages and thus it cannot receive the notification, at least not immediately. In the following, we will examine a case in which the terminal is switched off and a validity period of short message is defined (e.g. with parameter MVP, Message validity Period) in the short message service centre SMSC via which the notification message is to be transmitted. The validity period is a predetermined period, e.g. 24 hours. If the validity period of the short message expires, the short message service centre deletes the short message. If the terminal is not switched on before the validity period expires, the terminal does not receive the short message.